Probing the Broad-Spectrum Virus-Neutralizing Epitopes Using the High-Density Oligomannose-Conjugates and Carbohydrate Microarrays

Following global efforts to decipher the glycome of the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), we further explored the immunologically potent carbohydrates in the viral glycan shield. Specifically, we constructed a large panel of glycoconjugates, utilizing soluble protein carriers and bacteriophage Qβ viral-like particles (Qβ-VLPs) to display oligomannoses in multiple cluster configurations for immune recognition. Using a broad-spectrum virus-neutralizing agent, Galanthus nivalis agglutinin (GNA), and SARS-CoV-2-neutralizing antisera elicited in nonhuman primates (NHPs), we performed a carbohydrate-microarray-based glyco-epitope-mapping analysis of these synthetic glyco-conjugates. We found that several oligomannose-conjugates, including members of the Bovine Serum Albumin (BSA)- and Qβ-series of high-mannose-conjugates, reestablished the GNA epitopes with potency comparable to that of those expressed by the native viral glycoproteins. However, the NHP antisera differentially react with these glyco-conjugates and exhibit high selectivity for the GNA⁺-Qβ-VLPs. These findings suggest that the high-density oligomannose clusters presented by the Qβ-VLPs may resemble the virion-surface-exposed oligomannoses, thereby supporting glycan-specific immune recognition by antibodies elicited through natural infection.